Reproduction steps:
1. Open the “FrameTimeStripped“ project
2. Open the “SampleScene” scene
3. Enter Play Mode or Build And Run (enable Development Build to see errors in Player)
4. Fly around in the scene for up to a minute using W, A, S, D, Q, E, Left Shift, and RMB

Expected result: No errors, no significant frame time spikes
Actual result: Errors showcasing noticeable frame time spikes (e.g. from 2 to 20 ms)

Reproduced in: 2021.3.29f1, 2022.3.7f1, 2023.1.7f1, 2023.2.0b3

Reproduced on:
Windows 11 (240 Hz without G-SYNC),
Windows 11 (144 Hz with G-SYNC),
macOS 13.4.1 (Intel) (60 Hz without G-SYNC) but rarely

Not reproduced on: No other environment tested

Reporter’s notes: While developing a 2D platformer game, I've observed unpredictable and intermittent spikes in frame times. Typically, frame times maintain a consistent ~3-5 ms. However, approximately every 2-10 seconds, there is a noticeable spike in frame times up to 15-40 ms, resulting in a clear jitter during gameplay. This behavior persists even when there is no activity in the scene (no enemies, dynamic lighting, movement, or other real-time operations). Profiling results reveal no GC allocation per frame, no apparent scripting, rendering, or physics bottlenecks, and no dynamic loads/unloads during gameplay. The issue occurs no matter whether Incremental GC is enabled or disabled. To isolate the issue from my project's specific code or assets, I created a separate URP sample project (the Workbench project) and populated the scene with multiple assets to simulate a similar load. Interestingly, the same frame time spikes are observed. The issue is most consistent with a 240 Hz G-SYNC display

Related forum thread: https://forum.unity.com/threads/unexpected-frame-time-spikes.1468817/